1. Technical Field of the Invention
The present invention relates to a heating device capable of judging the cause of failure, a liquid processing apparatus using the heating device and a method of detecting the failure. For example, the invention relates to a liquid processing apparatus for applying a designated liquid processing on various kinds of substrates, such as semiconductor waters and LCD substrates.
2. Description of the Related Art
In the method of controlling the operation of a heater driven by electric power, there is known a method having the following steps of: connecting a sensor for detecting the temperature of an object to be processed to a temperature regulator; comparing a target temperature set in the temperature regulator with an actual temperature of the object to be processed; and transmitting ON/OFF signals to control the power supply for the heater for heating the object, from the temperature regulator to a solid state relay between a power source and the heater; whereby the heating operation of the heater can be switched on and off by the ON/OFF control for the solid state relay.
As the method of detecting a failure in the heater control circuit having the above solid state relay, there has been generally adopted a method of detecting whether the heater is breaking upon detection of a current flowing through the heater by a current transformer (CT).
In the above failure detecting method using the current transformer (CT), however, there is the possibility that other failures besides the breaking down of the heater, for example, breaking down of the solid state relay, failure of the contact such as magnet conductor in a power switch for the heater, etc. are regarded as the breaking down of the heater.
In the solid state relay, there is also known one equipped with a diagnostic function to detect the failure. However, this solid state relay is provided with little kinds and also expensive. Moreover, this solid state merely is capable of detecting its own malfunction and no more than. In this way, due to the impossibility of classifying the cause of failure in the heater control circuit finely, every time the heater control circuit is out of order, it is required to take measures, for example, inspecting of questionable parts, replacing of all parts, etc. Such measures are far from being desirable in the aspects of maintenance and cost.
Under the above-mentioned situation, the object of the present invention is to provide a heating device in which a heater control circuit has a plurality of built-in monitors allowing the failure in the circuit to be classified into every cause thereby to facilitate the measures against the failure in the superior maintenance. Further, the object of the invention is to provide a liquid processing apparatus using the heating device and also a failure detecting method for the heating device.
The first feature of the present invention resides in the provision of a heating device comprising:
a heater for heating an object to be heated;
a power supply circuit for supplying electric power from a power source to the heater;
a power switch for switching on and off a power output from the power source;
an output control circuit for controlling the power output from the power source to the heater;
a relay for switching on and off the operation of the power supply circuit in accordance with signals outputted from the output control circuit; and
a failure detecting circuit for detecting an operational failure of the heating device;
wherein the failure detecting circuit includes
a first monitor for monitoring the operation of an ON/OFF contact in the power switch;
a second monitor for detecting ON/OFF signals transmitted from the power control circuit to the relay; and
a third monitor for detecting an output voltage on a secondary side of the relay.
According to the second feature of the invention, the relay, the second monitor and the third monitor are formed by a solid state relay.
According to the third feature of the invention, the heating device further comprises a control board which displays an output of the first monitor, an output of the second monitor and an output of the third monitor respectively.
According to the fourth feature of the invention, the failure detecting circuit further includes a fourth monitor which includes a current transformer for detecting a current flowing through the heater and further generates the detected current in form of ON/OFF signals standardizing a constant threshold current value.
According to the fifth feature of the invention, the output control circuit includes:
a temperature sensor for detecting a temperature of the object to be heated; and
a temperature regulator in which a designated temperature is preset for the object and which generates ON/OFF signals to the relay upon comparing the detected temperature of the object with the designated temperature.
According to the sixth feature of the invention, there is further provided a liquid processing apparatus comprising:
a liquid processing unit which supplies an object to be processed with a processing liquid thereby to carry out a liquid processing;
a processing-liquid supplying unit to supply the heated processing liquid to the liquid processing unit; and
a heating unit for heating the processing liquid to a predetermined temperature;
wherein the heating unit includes:
a heater for heating the processing liquid;
a power supply circuit for supplying the heater with an electric power from a power source;
a power switch for switching on and off a power output from the power source;
an output control circuit for controlling the power output supplied from the power source to the heater;
a relay for switching on and off the operation of the power supply circuit in accordance with signals generated from the output control circuit; and
a failure detecting circuit for detecting an operational failure of the heating unit; and
the failure detecting circuit includes:
a first monitor for monitoring the operation of an ON/OFF contact in the power switch;
a second monitor for detecting ON/OFF signals transmitted from the power control circuit to the relay; and
a third monitor for detecting an output voltage on a secondary side of the relay.
According to the seventh feature of the invention, the failure detecting circuit of the above liquid processing apparatus further includes a fourth monitor which includes a current transformer for detecting a current flowing through the heater and further generates the detected current in form of ON/OFF signals standardizing a constant threshold current value.
According to the eighth feature of the invention, the output control circuit of the above liquid processing apparatus includes:
a temperature sensor for detecting a temperature of the processing liquid; and
a temperature regulator in which a designated temperature is preset for the processing liquid and which generates ON/OFF signals to the relay upon comparing the detected temperature of the processing liquid with the designated temperature.
According to the ninth feature of the invention, the failure detecting circuit of the above liquid processing apparatus includes an overheat monitor which monitors both a temperature of the processing liquid and a temperature of the heater thereby to detect whether the processing liquid is overheated or not.
According to the tenth feature of the invention, the liquid processing apparatus further comprises an ON/OFF switch interposed in a wiring between the output control circuit and a primary side of the relay.
According to the eleventh feature of the invention, the liquid processing apparatus further comprises an interlocking circuit which turns the power switch off when the quantity of the processing liquid to be heated is less than a predetermined quantity.
According to the twelfth feature of the invention, the processing-liquid supplying unit of the liquid processing apparatus includes:
a tank having the processing liquid stored therein, the tank being equipped with the heater;
a supply pipe through which the processing liquid is supplied from the tank to the liquid processing unit; and
a collecting pipe for collecting the processing liquid which has been used in the liquid processing unit, into the tank.
According to the thirteenth feature of the invention, the tank has an inner tank and an outer tank in double structure and the collecting pipe is connected to the outer tank. Further, the heater is arranged in the periphery of the outer tank.
According to the fourteenth feature of the invention, the output control circuit includes:
a temperature sensor arranged in the outer tank to detect the temperature of the processing liquid; and
a temperature regulator in which a designated temperature is preset for the processing liquid and which generates ON/OFF signals to the relay upon comparing the detected temperature of the processing liquid with the designated temperature, and
the output control circuit controls so that the temperature of the processing liquid in the outer tank is maintained to the designated temperature.
According to the fifteenth feature of the invention, the processing-liquid supply unit of the liquid processing apparatus has a tank having the processing liquid stored therein, the tank being equipped with the heater. Further, the liquid processing apparatus further comprises a level sensor disposed in the tank to detect a level of the processing liquid stored in the tank and an interlocking circuit which turns the power switch off when the quantity of the processing, liquid to be heated is less than a predetermined quantity.
According to the sixteenth feature of the invention, there is further provided a failure detecting method of detecting a circuit failure in a heating device, the heating device having a power supply circuit connecting a power source to a heater, an ON/OFF contact arranged in the power supply circuit and also operated by a power switch to supply the heater with electric power and a relay arranged in the power supply circuit to control the power supply for the heater intermittently, the method comprising the step of:
in case of turning the power switch off,
detecting at least one of the operation of the ON/OFF contact, the ON/OFF state of an output voltage on a secondary side of the relay and the ON/OFF state of a current in the power supply circuit; and
judging whether the ON/OFF contact has a failure, on a basis of a result of the detecting step.
According to the seventeenth feature of the invention, there is provided another failure detecting method of detecting a circuit failure in a heating device, the heating device having a relay arranged in a power supply circuit connecting a power source to a heater, for controlling the power supply for the heater intermittently, the method comprising the step of:
detecting the ON/OFF state of an input signal on a primary side of the relay and the ON/OFF state of an output voltage on a secondary side of the relay; and
judging whether the relay is subjected to snapping or short-circuit, on a basis of a result of the detecting step.
According to the eighteenth feature of the invention, the above failure detecting method further comprises the step of detecting the ON/OFF state of a current flowing through the power supplying circuit, whereby the snapping of the heater can be detected on a basis of a result of the detecting step.
With the constitution mentioned above, in the heating device of the present invention and the liquid processing apparatus using the heating device, since they are commonly provided with various monitors as xe2x80x9cbuilt-inxe2x80x9d failure detecting means, the failures in the heater, the power supply circuit and the output control means can be judged for every cause, for example, snapping of the heater, snapping or short-circuit in the solid state relay, abnormality in the power source for the heater, etc. Accordingly, even if the heating device and the liquid processing apparatus are out of order, the recovery/measures against the malfunction is facilitated thereby to improve both heating controllability and maintenance of the device and apparatus. Additionally, since these monitors serving as the failure detecting means do not require any expensive parts, there is no possibility to cause the increasing of device/apparatus cost,